40 J. A. Bentley 



Dr. Kefford: I would like to make my comments rather generally 

 in the field of natural auxins, and I do this because I feel that the 

 technique that Prof. Bennet-Clark and I have pioneered and which 

 we felt would be of great assistance in helping to clarify our thoughts 

 on natural auxins has now become a curse. Not only has it revealed 

 numerous substances in plant extracts which can produce a growth 

 reaction, but it appears that the very act of chromatography itself 

 can produce new compounds. It has become apparent that we can't 

 avoid the very tedious task of having to isolate and identify the com- 

 pounds that turn up on chromatograms. But since this is a tedious 

 task, I think it is up to us to make some efforts to decide which are 

 the physiologically interesting substances that appear on our chroma- 

 tograms. It is becoming aj)parent that unless Ave are dealing with a 

 reaction of rather rare promiscuity, not all these substances which are 

 able to make Avena sections grow are acting at the same reaction 

 site. So I would suggest that the first step in helping us to limit the 

 field of substances which we must identify would be to know some- 

 thing about the primary site of action of these substances. And if 

 we are going to be interested in compounds that are active in corre- 

 lation j)henomena, we must be concerned with those that can be 

 transported through the plant. And here, at least in the auxin trans- 

 port system, we have a reaction with, at last, a respectable chemical 

 specificity. To date, in the published data there is only one contender 

 for a natural substance that is transported, and that is indole-3-acetic 

 acid. So I would suggest that maybe tests which tell us something 

 about the transport of these substances would help us to limit the 

 field. 



Dr. Thimann: A\'hen you hydrolyze the aqueous fractions with al- 

 kali to get the auxins, do you get both X and Z, or do you only get 

 X, or do you get indole-3-acetic acid only? 



Dr. Bentley: No, you get substantially the same pictures as with 

 the acidic eiher extract. You get both X and Z and you can demon- 

 strate this interchangcability. I wouldnt say categorically that they 

 are the same compounds, but they do behave the same and show the 

 same incomiKitibility. There's no more evidence for the presence of 

 indole-3-acetic add in tlie substance we obtained from the aqueous 

 fraction, lii.ni lioiii ihc ether liactioii. On ihe subject of transjjort 

 whidi 1)1. Kelloid raised, there are other people here more qualified 

 than 1 am to s|)eak on ilie gibberellins. but I believe that they don't 

 show ihis polar iiansport. And il we have the gibberellins involved, 

 then we li;ivc to think even fuiihc i ih;in just looking for polar trans- 

 port, in our (OMi]>()un(l. 



